Birth and Family Background:
Abu Ja’far Muhammad Ibn Hassan Tusi, known as “Sheikh al-Tayefah” in the Iranian province of Khorassan, was born in the year 385 A.H.
He was one of the very bright luminaries of the Islamic world. He has written many books on the various subjects of Fiqh (Islamic Jurisprudence), Osool (Fundamental Principles of Fiqh), Hadith (Sayings of the Holy Prophet (s.a.) and his infallible household), Tafseer (Exegesis on the holy Koran), Kalaam (Theology) and Rijal (Genealogies of Narrators of Hadiths).
Sheikh Tusi belonged to a family that produced generations of Islamic Scholars and Jurisprudents.
His son, Sheikh Abu Ali, was an outstanding Islamic Jurisprudent as well. According to the book “Mustadrak al-Wasa’il” Volume 3, P.498, Sheikh Abu Ali had to his credit a book entitled “Amaali”. He also contributed an explanatory work on “Al-Nihayeh”, a book authored by his father.
According to another book entitled “Lolo al-Bahrain”, daughters of Sheikh Tusi, too, were Islamic Jurisprudents and scholars in their own right.
Sheikh Abu Ali had a son named Sheikh Abul-Hassan who succeeded him as the religious authority and chairman of the Islamic Theological Center (Hawzah 'Ilmiyyah). 'Imad Tabari' eulogized him by saying that, "…Had it been permitted to recite “Salawat” (a formula of invocation to God through which praise of His Messengers is conveyed) for anyone other than the divine prophets, I would have uttered it in respect of Sheikh Abu Ali, as well". Sheikh Abu Ali died in the year 540 A.H.

Sheikh Tusi’s Education:
At the age of 23 in the year 408 A.H. Sheikh Tusi emigrated to Baghdad and remained in Iraq up until his death.
After the death of his mentor, Sayyed Mortadha Alamul-Hoda, he succeeded him as the chairman of the Theological Center as well as the Shiite authority competent to issue religious decrees (Fatwa).
Sheikh Tusi has been a student of Sheikh Mofeed for five years. Also for many more years he has been taught by Sheikh Mofeed’s brilliant pupil, Sayyed Mortadha.
Sheikh Tusi remained in Baghdad for a period of twelve years after the demise of his teacher, Sayyed Mortada in 436 A.H.
A series of invasions soon afterwards caused destruction of his house and his shifting to Najaf, where he established the Najaf Theological Center (Hawzah). He died in Najaf in the year 460 A.H. His grave there is well known.

His Personality and Intellectuality:
Sheikh Tusi’s book on Fiqh (Islamic Jurisprudence) entitled “Al-Nihayeh” was formerly used as a textbook in the theological schools and seminaries. He wrote another book entitled “Al-Mabsut”, which brought Islamic Fiqh to a new stage and was accounted the most comprehensive one at its age.
Among his other books on Fiqh, “Al-Khilaf” is notable in that it offers the opinions of not only the Shiite, but also the Sunnite scholars.
There are more books on Fiqh written by Sheikh Tusi. Ancient scholars – until about one century ago –used to mention just “Sheikh” in matters of Fiqh, by which they invariably meant “Sheikh Tusi”; and whenever they referred to the “Sheikhs”, they meant "Sheikh Mofeed and Sheikh Tusi". No doubt, Sheikh Tusi is among a few distinguished Islamic Jurisprudents whose names will shine in the history forever.

His Leadership of the Shiites:
As mentioned earlier, after the death of Sayyed Mortadha Alamul-Hoda, Sheikh Tusi became the leader of the Shiites. Then his residence at Karkh, Baghdad turned into an asylum and cynosure for Muslims. Many of the Ulema (Islamic scholars) and intellectuals, coming from far-flung places of the Islamic world, sought the presence of Sheikh Tusi. They felt honored as participants in his sessions and even as his students, and benefited from the illuminating words of that divine sage. The number of his students totaled more than three hundred. A few hundred Sunnite Ulema, too, benefited from his presence.

His Higher Appointments:
Sheikh Tusi’s reputation in the realm of Islamic knowledge and learning, as well as his personal fame as a man of piety and devoutness, soon circulated around the world of Islam, and even penetrated the palace of "Al-Ghaem Billah" - the Abbasid Caliph. The Caliph was so impressed by Sheikh Tusi’s fame as a learned man that he, with the concurrence of the Buyid Dynasty, appointed the Sheikh to the court’s chair of teaching Kalaam (Theology) in Baghdad. Those days that Chair carried immense prestige, since only the most distinguished Ulema were appointed to it. This higher appointment showed that Sheikh Tusi was recognized as the most qualified savant of Baghdad for the teaching post.

The Most Regrettable Event:
In the year 447 A.H. the Seljuk Turks took advantage of the weakness of the Buyid Dynasty. They invaded Baghdad; and after deposing the incumbent government, occupied the city. Subsequently Abdul-Malek, a prejudiced minister of Tugrol Baik, launched an attack on the residential locality of the Shiites, which resulted in killing of residents and destruction of their properties. The residence of Sheikh Tusi was also attacked with the intention of killing him, but he was not found at home. His residence, its contents, including his books, were pillaged and burnt. After this most regrettable event, which caused irreparable loss of Sheikh Tusi’s books, he had to leave Baghdad and go to live at Najaf Ashraf, which was then a small village where Shiites lived in the vicinity of the Holy Shrine of Imam Ali (a.s.).
After the turmoil by the invaders subsided, Sheikh Tusi founded a seminary at Najaf Ashraf, which subsequently became one of the most important centers of Shiite learning.

Sheikh Tusi’s Writings:
Of the four authoritative resources of the Shiites, two are written by Sheikh Tusi. These two basic reference books are: “Tahdhib al-Ahkam” and “Al-Istibsar”. Both of these pertain to Hadiths/narrations of Islamic Jurisprudential decrees and injunctions.
Some other compilations of Sheikh Tusi are as follows:
“Al-Nihayeh” 2)“Al-Mabsoot”
“Al-Khilaf” 4) “Iddatul-Osool”
“Al-Rijal” 6) “Al-Fehrist”
“Tamhidul-Osool” 8) “Al-Tibyan”

His Death:
The honorable Sheikh Tusi passed away in the night of Monday, the 22nd of Moharram, 460 A.H.
His body was buried in the precincts of his own residence at Najaf Ashraf. The world of Islam lost one of the most memorable Jurisprudents; and history has yet to witness a comparable personality. Our Islamic Jurisprudents still benefit from his illuminating works. His residence is now being used as a mosque.